Add a histogram to measure browser window display

chrome/common/startup_metric_utils.h

+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_COMMON_STARTUP_METRIC_UTILS_H_
+#define CHROME_COMMON_STARTUP_METRIC_UTILS_H_
+
+// Utility functions to support metric collection for browser startup.
+
+class StartupMetricUtils {

[sky, 2012/07/25 15:51:48]

No need to for a class here, use functions.

[jeremy, 2012/07/26 12:57:26]

Done.

+ public:
+  // Returns true if any UI other than the browser window has been displayed
+  // so far.  Useful to test if UI has been displayed before the first browser
+  // window was shown, which would invalidate any surrounding timing metrics.
+  static bool WasNonBrowserUIDisplayed();
+
+  // Call this when displaying UI that might potentially delay the appearance
+  // of the initial browser window on Chrome startup.
+  //
+  // Note on usage: This function is idempotent and its overhead is low enough
+  // in comparison with UI display that it's OK to call it on every
+  // UI invocation regardless of whether the browser window has already
+  // been displayed or not.
+  static void SetNonBrowserUIDisplayed();
+};
+
+#endif  // CHROME_COMMON_STARTUP_METRIC_UTILS_H_